The Key Factor by Paul Aitman is a very useful program aimed at improving your mastery of the keyboard - and cleverly disguised as a space invaders game.
Having selected the level of play the screen clears and battle commences. Your laser bases are represented by eight squares at the bottom of the screen, each containing a letter or symbol from the keyboard. Above your bases are numerous shields, which are eroded each time an alien escapes your fire and touches the shield.
Missiles are fired by pressing any of the keys displayed. On the lower levels this doesn't present too many problems as the symbols at the bottom of the screen don't change until that particular missile has been fired. However, as you improve and reach the higher levels you may notice that although you appear to be pressing the correct keys there are no little missiles soaring skywards and annihilating the baddies. This is because the symbols are changing constantly, so if you dawdle before hitting the correct key you will find that it has already changed to a new symbol.
All of the aliens are displayed in glorious colour and great detail. Paul Airman has obviously taken great care and it shows. A well-presented and fun way to find your way around the keyboard.